It is important for rubbery polymers that are used in tires, hoses, power transmission belts and other industrial products to have good compatibility with fillers, such as carbon black and silica. To attain improved interaction with fillers such rubbery polymers can be functionalized with various compounds, such as amines. U.S. Pat. No. 4,935,471 discloses a process for preparing a polydiene having a high level of affinity for carbon black which comprises reacting a metal terminated polydiene with a capping agent selected from the group consisting of (a) halogenated nitriles having the structural formula Xxe2x80x94Axe2x80x94Cxe2x89xa1N, wherein X represents a halogen atom and wherein A represents an alkylene group containing from 1 to 20 carbon atoms, (b) heterocyclic aromatic nitrogen containing compounds, and (c) alkyl benzoates. The capping agents disclosed by U.S. Pat. No. 4,935,471 react with metal terminated polydienes and replace the metal with a terminal cyanide group, a heterocyclic aromatic nitrogen containing group or a terminal group which is derived from an alkyl benzoate. For example, if the metal terminated polydiene is capped with a nitrile, it will result in the polydiene chains being terminated with cyanide groups. The use of heterocyclic aromatic nitrogen containing compounds as capping agents can result in the polydiene chains being terminated with a pyrrolyl group, an imidazolyl group, a pyrazolyl group, a pyridyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an indolizinyl group, an isoindolyl group, a 3-H-indolyl group, a cinnolinyl group, a pyridinyl group, a .beta.-carbolinyl group, a perimidinyl group, a phenanthrolinyl group or the like.
U.S. Pat. No. 4,935,471 also discloses that lithium amides are highly preferred initiators because they can be used to prepare polydienes which are terminated with polar groups at both ends of their polymer chains. The extra polar functionality provided by lithium amides results in increased interaction with carbon black resulting in better polymer-carbon black dispersion. The lithium amides disclosed by U.S. Pat. No. 4,935,471 include lithium pyrrolidide. U.S. Pat. No. 4,935,471 also indicates that preferred initiators include amino alkyl lithium compounds of the structural formula: 
wherein A represents an alkylene group containing from 1 to 20 carbon atoms, and wherein R1 and R2 can be the same or different and represent alkyl groups containing from 1 to 20 carbon atoms.
It is also desirable for synthetic rubbers to exhibit low levels of hysteresis. This is particularly important in the case of rubbers that are used in tire tread compounds. Such polymers are normally compounded with sulfur, carbon black, accelerators, antidegradants and other desired rubber chemicals and are then subsequently vulcanized or cured into the form of a useful article. It has been established that the physical properties of such cured rubbers depend upon the degree to which the carbon black is homogeneously dispersed throughout the polydiene rubber. This is in turn related to the level of affinity that carbon black has for the rubber. This can be of practical importance in improving the physical characteristics of rubber articles that are made utilizing polydiene rubbers. For example, the rolling resistance and tread wear characteristics of tires can be improved by increasing the affinity of carbon black to the rubbery polymers utilized therein. Therefore, it would be highly desirable to improve the affinity of a given polydiene rubber for carbon black and/or silica. This is because a better dispersion of carbon black throughout polydiene rubbers which are utilized in compounding tire tread compositions results in a lower hysteresis value and consequently tires made therefrom have lower rolling resistance. It is also known that a major source of hysteresis is due to polymer chain ends that are not capable of full elastic recovery. Accordingly, improving the affinity of the rubber chain ends to the filler is extremely important in reducing hysteresis.
U.S. Pat. No. 6,080,835 discloses a functionalized elastomer comprising: a functional group defined by the formula: 
where R1 is a selected from the group consisting of a divalent alkylene group, an oxy-alkylene group, an amino alkylene group, and a substituted alkylene group, each group having from about 6 to about 20 carbon atoms, R2 is covalently bonded to the elastomer and is selected from the group consisting of a linear-alkylene group, a branched-alkylene group, and a cyclo-alkylene group, each group having from about 2 to about 20 carbon atoms.
U.S. Pat. No. 5,932,662 discloses a method of preparing a polymer comprising: preparing a solution of one or more anionically polymerizable monomers in a solvent; and, polymerizing under effective conditions, said monomers in the presence of a polymerization initiator having the formula 
wherein R1 is a divalent alkylene, an oxy- or amino-alkylene having from 6 to about 20 carbon atoms; and, R2 is a linear-alkylene, branched-alkylene, or cyclo-alkylene having from about 2 to about 20 carbon atoms, Li is a lithium atom bonded directly to a carbon atom of R2; and R3 is a tertiary amino, an alkyl having from 1 to about 12 carbon atoms; an aryl having from about 6 to about 20 carbon atoms; an alkaryl having from about 7 to about 20 carbon atoms; an alkenyl having from about 2 to about 12 carbon atoms; a cycloalkyl having from about 5 to about 20 carbon atoms; a cycloalkenyl having from about 5 to about 20 carbon atoms; a bicycloalkyl having from about 6 to about 20 carbon atoms; and, a bicycloalkenyl having from about 6 to about 20 carbon atoms; where n is an integer of from 0 to about 10.
U.S. Pat. No. 6,084,025 discloses a functionalized polymer prepared by a process comprising the steps of: preparing a solution of a cyclic amine compound, an organolithium compound, and from 3 to about 300 equivalents, based upon one equivalent of lithium, of a monomer selected from vinyl aromatic monomers, and mixtures thereof, where said cyclic amine compound is defined by the formula 
where R2 is selected from the group consisting of an alkylene, substituted alkylene, bicycloalkane, and oxy- or N-alkylamino-alkylene group having from about 3 to about 16 methylene groups, N is a nitrogen atom, and H is a hydrogen atom, thereby forming a polymerization initiator having the formula A(SOL)yLi, where Li is a lithium atom, SOL is a divalent hydrocarbon group having from 3 to about 300 polymerized monomeric units, y is from 0.5 to about 3, and A is a cyclic amine radical derived from said cyclic amine; charging the solution containing A(SOL)yLi with from about 0.01 to about 2 equivalents per equivalent of lithium of a chelating reagent, and an organic alkali metal compound selected from compounds having the formula R4OM, R5C(O)OM, R6R7NM, and R8SO3M, where R4, R5, R6, R7, and R8 are each selected from alkyls, cycloalkyls, alkenyls, aryls, or phenyls, having from 1 to about 12 carbon atoms; and where M is Na, K, Rb or Cs, and sufficient monomer to form a living polymeric structure; and quenching the living polymeric structure.
In the initiator systems of U.S. Pat. No. 6,084,025 a chelating reagent can be employed to help prevent heterogeneous polymerization. The reagents that are reported as being useful include tetramethylethylenediamine (TMEDA), oxolanyl cyclic acetals, and cyclic oligomeric oxolanyl alkanes. The oligomeric oxolanyl alkanes may be represented by the structural formula: 
wherein R9 and R10 independently are hydrogen or an alkyl group and the total number of carbon atoms in xe2x80x94CR9R10-ranges between one and nine inclusive; y is an integer of 1 to 5 inclusive; yxe2x80x2 is an integer of 3 to 5 inclusive; and R11, R12, R13, and R14 independently are xe2x80x94H or xe2x80x94CnH2n+1, wherein n=1 to 6.
U.S. Pat. No. 6,344,538 discloses functionalized monomers and polymerized functionalized monomers selected from the group consisting of 2-(N,N-dimethylaminomethyl)-1,3-butadiene, 2-(N,N-diethylaminomethyl)-1,3-butadiene, 2-(N,N-di-n-propylaminomethyl)-1,3-butadiene, 2-(cyanomethyl)-1,3-butadiene, 2-(aminomethyl)-1,3-butadiene, 2-(hydroxymethyl)-1,3-butadiene, 2-(carboxymethy)-1,3-butadiene, 2-(acetoxymethyl)-1,3-butadiene, 2-(2-alkoxy-2-oxoethyl)-1,3-butadiene, 2,3-bis(cyanomethyl)-1,3-butadiene, 2,3-bis(dialkylaminomethyl)-1,3-butadiene, 2,3-bis(4-ethoxy-4-4-oxobutyl)-1,3-butadiene and 2,3-bis(3-cyanopropyl)-1,3-butadiene, and methods for preparing such functionalized diene monomers and polymers.
The present invention relates to functionalized monomers that can be polymerized into rubbery polymers having low hysteresis and good compatibility with fillers, such as carbon black and silica. The functionalized monomers of this invention are typically incorporated into the rubbery polymer by being copolymerized with one or more conjugated diolefin monomers and optionally other monomers that are copolymerizable therewith, such as vinyl aromatic monomers. In any case, improved polymer properties are realized because the functionalized monomers of this invention improve the compatibility of the rubber with the types of fillers that are typically used in rubber compounds, such as carbon black and silica.
This invention more specifically discloses monomers that are particularly useful for copolymerization with conjugated diolefin monomers to produce rubbery polymers having better compatibility with fillers. The monomers of this invention have a structural formula selected from the group consisting of 
wherein n represents an integer from 4 to about 10, 
wherein n represents an integer from 0 to about 10 and wherein m represents an integer from 0 to about 10, with the proviso that the sum of n and m is at least 4; 
wherein R and Rxe2x80x2 can be the same or different and represent alkyl, allyl groups or alkoxy groups containing from 1 to about 10 carbon atoms; 
wherein n represents an integer from 1 to about 10, and wherein R and Rxe2x80x2 can be the same or different and represent alkyl groups containing from 1 to about 10 carbon atoms; 
wherein n represents an integer from 1 to about 10 and wherein m represents an integer from 4 to about 10; 
wherein x represents an integer from 1 to about 10, wherein n represents an integer from 0 to about 10 and wherein m represents an integer from 0 to about 10, with the proviso that the sum of n and m is at least 4; 
wherein R and Rxe2x80x2 can be the same or different and represent allyl, alkoxyl or alkyl groups containing from 1 to about 10 carbon atoms, 
wherein m represents an integer from about 4 to about 10; 
wherein R represents a hydrogen atom or an alkyl group containing from 1 to about 10 carbon atoms, wherein n represents an integer from 0 to about 10, and wherein m represents an integer from 0 to about 10, with the proviso that the sum of n and m is at least 4; and 
wherein n represents an integer from 0 to about 10, wherein m represents an integer from 0 to about 10, wherein x represents an integer from 1 to about 10, and wherein y represents an integer from 1 to about 10.
One aspect of this invention is based upon the unexpected finding that random copolymers of 1,3-butadiene monomer and 3-(2-pyrrolidinoethyl)styrene and/or 4-(2-pyrrolidinoethyl) styrene having a low vinyl content can be synthesized by anionic polymerization at normal polymerization temperatures without the need for a conventional polar modifier.
The subject invention more specifically discloses a process for synthesizing a rubbery polymer that comprises copolymerizing at least one conjugated diolefin monomer and at least one functionalized monomer in an organic solvent at a temperature which is within the range of 20xc2x0 C. to about 100xc2x0 C., wherein the polymerization is initiated with an anionic initiator, wherein the functionalized monomer is of the structural formula: 
wherein n represents an integer from 4 to about 10, and wherein the polymerization is conducted in the absence of conventional polar modifiers.
The subject invention further discloses a process for synthesizing a rubbery polymer that comprises copolymerizing at least one conjugated diolefin monomer and at least one functionalized monomer in an organic solvent at a temperature which is within the range of 20xc2x0 C. to about 100xc2x0 C., wherein the polymerization is initiated with an anionic initiator, and wherein the functionalized monomer has a structural formula selected from the group consisting of 
wherein n represents an integer from 4 to about 10, 
wherein n represents an integer from 0 to about 10 and wherein m represents an integer from 0 to about 10, with the proviso that the sum of n and m is at least 4; 
wherein n represents an integer from 1 to about 10, and wherein R and Rxe2x80x2 can be the same or different and represent alkyl groups containing from 1 to about 10 carbon atoms; 
wherein n represents an integer from 1 to about 10 and wherein m represents an integer from 4 to about 10; 
wherein x represents an integer from 1 to about 10, wherein n represents an integer from 0 to about 10 and wherein m represents an integer from 0 to about 10, with the proviso that the sum of n and m is at least 4; 
wherein R represents a hydrogen atom or an alkyl group containing from 1 to about 10 carbon atoms, wherein n represents an integer from 0 to about 10, and wherein m represents an integer from 0 to about 10, with the proviso that the sum of n and m is at least 4; and and 
wherein n represents an integer from 0 to about 10, wherein m represents an integer from 0 to about 10, wherein x represents an integer from 1 to about 10, and wherein y represents an integer from 1 to about 10.
The subject invention further reveals a tire which is comprised of a generally toroidal-shaped carcass with an outer circumferential tread, two spaced beads, at least one ply extending from bead to bead and sidewalls extending radially from and connecting said tread to said beads, wherein said tread is adapted to be ground-contacting, and wherein said tread is comprised of (I) a filler, and (II) rubbery polymer which is comprised of repeat units that are derived from (1) at least one conjugated diolefin monomer, and (2) at least one monomer having a structural formula selected from the group consisting of 
wherein n represents an integer from 4 to about 10, 
wherein n represents an integer from 0 to about 10 and wherein m represents an integer from 0 to about 10, with the proviso that the sum of n and m is at least 4; 
wherein R and Rxe2x80x2 can be the same or different and represent allyl groups or alkoxy groups containing from 1 to about 10 carbon atoms; 
wherein n represents an integer from 1 to about 10, and wherein R and Rxe2x80x2 can be the same or different and represent alkyl groups containing from 1 to about 10 carbon atoms; 
wherein n represents an integer from 1 to about 10 and wherein m represents an integer from 4 to about 10; 
wherein x represents an integer from 1 to about 10, wherein n represents an integer from 0 to about 10 and wherein m represents an integer from 0 to about 10, with the proviso that the sum of n and m is at least 4; 
wherein R and Rxe2x80x2 can be the same or different and represent alkyl groups containing from 1 to about 10 carbon atoms, 
wherein m represents an integer from about 4 to about 10; 
wherein R represents a hydrogen atom or an alkyl group containing from 1 to about 10 carbon atoms, wherein n represents an integer from 0 to about 10, and wherein m represents an integer from 0 to about 10, with the proviso that the sum of n and m is at least 4; and and 
wherein n represents an integer from 0 to about 10, wherein m represents an integer from 0 to about 10, wherein x represents an integer from 1 to about 10, and wherein y represents an integer from 1 to about 10.
The present invention further discloses a process for synthesizing an amino ethyl styrene monomer which comprises: (1) reacting divinyl benzene with a cyclic amine in a reacting mixture in the presence of an alkyl lithium compound at a temperature which is within the range of xe2x88x9280xc2x0 C. to 80xc2x0 C. to produce the amino ethyl styrene; and (2) deactivating the alkyl lithium compound by adding an alcohol or water to the reaction mixture containing the amino ethyl styrene. This process is preferable conducted at a temperature which is within the range of about xe2x88x9220xc2x0 C. to about 50xc2x0 C. and is most preferable conducted at a temperature is within the range of about xe2x88x9210xc2x0 C. to about 25xc2x0 C. The alkyl lithium compound is typically present at a level which is within the range of about 0.5 mole percent to about 5 mole percent, based upon the molar amount of cyclic amine present. The alkyl lithium compound is preferably present at a level which is within the range of about 1 mole percent to about 4 mole percent and is more preferably present at a level which is within the range of about 1.5 mole percent to about 2.5 mole percent, based upon the molar amount of cyclic amine present.